EUGENE, Ore. _ Had Oregon coach Mike Bellotti known what fifth-string quarterback Darron Thomas was able to accomplish, he would have put the freshman in earlier against Boise State yesterday.

As it was, Thomas didn't come in quite soon enough for the Ducks to defeat the Broncos — who won 37-32. He nearly led Oregon to a comeback, completing 13 of 25 passes for 210 yards and three touchdowns, all in the fourth quarter.

Oregon (3-1) had wanted to redshirt Thomas, but injuries forced Bellotti to reconsider.

"We talked about it at halftime, but didn't get to it until the fourth quarter. That was a mistake," the coach said. "He did a great job, which I thought he could. We decided at halftime to bring him in, but we didn't do it until I said we could, and we probably should have done it earlier."

The trouble for Oregon's quarterbacks started before the season got under way.

The season's projected starter, Nate Costa, went down with a knee injury in the final days of fall practice and had season-ending surgery.

Backup Justin Roper learned he would be the starter in the week leading up to the season opener against Washington. When he suffered a concussion in the victory over the Huskies, and the Ducks went with both junior college transfer Jeremiah Masoli and freshman Chris Harper.

Roper returned to start the next two games, but then injured his left knee late in Oregon's 32-26 double-overtime victory over Purdue.

Masoli, Oregon's third-string quarterback going into the season, started against Boise State before leaving the game in the first quarter with a mild concussion.

When Harper, used more as a scrambler than a passer in Oregon's spread-option offense, was unable to do much against the Broncos, it became clear the Ducks would have to look at another option.

That was Thomas.

"They told in the second half to get ready so I was just waiting on the call," he said.

The Broncos led 37-13 at the end of the third quarter. Thomas first hit Jeff Maehl with a 24-yard scoring pass, and then found Ed Dickson with a 19-yard TD pass to narrow it to 37-26.

Thomas found Dickson again in the end zone to close to within 37-32 with 2:07 left in the game. But time ran out for the Ducks.

"We wanted the ball back one more time," Thomas said. "We knew what we were capable of doing."

The Broncos were clearly taken aback by the move.

"They made that quarterback change and started chucking it all over, and that hurt us a little bit," coach Chris Petersen said. "But I don't think Oregon was totally able to play the game they wanted to play, but the game they played we were able to play with them. So it worked out well for the Broncos."

Boise State (3-0) earned its first victory on the road over a BCS-conference team, and popped into The Associated Press poll at No. 19.

The Ducks, ranked No. 17 going into the game, dropped out of the top 25 with the loss.

Masoli's concussion was mild and he wasn't expect to miss time. Roper will likely miss Oregon's next game against Washington State. The team hopes to have him back for a trip to top-ranked Southern California on Oct. 4.

Bellotti said the team would assess its future this week.

"Going into Monday, we've got three quarterbacks and I assume they will all be ready to play," he said. "It will be an open competition and I think we will evaluate from there."